Three phase medium voltage power conversion system for closed-loop applications

Abstract

A three phase medium voltage power conversion system for closed-loop applications comprising a 3L-NPC converter. The switching system of the 3L-NPC converter is based on SHE-PWM patrons. The regulation system of the 3L-NPC converter comprises a controller and an interface module between the controller and the switching system which is configured for supplying to the switching system voltage reference samples at a rate L times faster than the rate of voltage reference samples managed by the controller.

The invention claimed is: 
     
       1. A three phase Medium Voltage (MV) power conversion system for coupling, in a close-loop mode, a power consuming device to a power source through a three level Neutral-Point-Clamped (3L-NPC) converter having a regulation system with a controller and a switching system, wherein:
 the switching system is based on Selective Harmonic Elimination-Pulse Width Modulation (SHE-PWM) patterns; and 
 said power conversion system further comprises an interface module between the controller and the switching system, wherein the interface module comprises means for predicting voltage reference values for L−1 (L minus one) samples based on factors consisting of a defined number M of reference samples previously supplied by the controller and a voltage reference value of each of the M number of reference samples previously supplied at a defined sample time interval of the controller from an initial time k, representing a time when a first of the M number of reference samples was supplied by the controller, to a current time, 
 wherein the switching system is supplied with an L-times faster rate of the previously supplied reference samples and wherein the controller is executed just once to supply the predicted voltage reference values for the L−1 samples such that harmonics in a load produced by the system is reduced as compared with harmonics that would be produced in the load if the controller were executed multiple times to supply voltage reference values for each of the L−1 samples. 
 
     
     
       2. The three phase Medium Voltage (MV) power conversion system according to  claim 1 , wherein the 3L-NPC converter comprises two DC capacitors and wherein the controller is configured with an Equalization Model (EM) approach for injecting a Second Order Negative Sequence (SONS) current in the 3L-NPC converter when voltages of the two DC capacitors are not balanced, iteratively in order to balance the voltages. 
     
     
       3. A three phase Medium Voltage (MV) power conversion system, comprising
 a power consuming device; 
 a three level Neutral-Point-Clamped converter (3L-NPC converter); 
 a regulation system, the regulation system comprising a controller and an interface module; 
 a switching system, the switching system is based on Selective Harmonic Elimination-Pulse Width Modulation (SHE-PWM) patterns; and 
 a power source 
 wherein the power consuming device is connected with the controller and with the 3L NPC converter, 
 wherein the interface module receives samples of voltage reference from the controller, and a sampling interval of the controller is Ts, 
 wherein the interface module comprising means for predicting voltage reference values for L−1 (L minus one) samples based on factors consisting of a defined number M of reference samples previously supplied by the controller and a voltage reference value of each of the M number of reference samples previously supplied at a defined sample time interval of the controller from an initial time k, representing a time when a first of the M number of reference samples was supplied by the controller, to a current time, and wherein the interface module sends to the switching system samples of the voltage reference at a rate L times as fast as a sampling rate of the controller, whereby reducing harmonics in an execution load L times, where L−1 is a number of additional samplings performed in the sampling interval (Ts) of the controller. 
 
     
     
       4. The three phase Medium Voltage (MV) power conversion system according to  claim 3 , wherein the interface module supplies to the switching system L−1 samples for each of the samples of voltage reference received from the controller that are generated according to a predictive model based on historic information. 
     
     
       5. The three phase Medium Voltage (MV) power conversion system according to  claim 4 , wherein the 3L-NPC converter comprises two DC capacitors and wherein the controller is configured accordingly with the Equalization Model (EM) approach for injecting a Second Order Negative Sequence (SONS) current in the 3L-NPC converter when voltages of the two DC capacitors are not balanced, iteratively in order to balance the voltages. 
     
     
       6. The three phase Medium Voltage (MV) power conversion system according to  claim 3 , wherein the 3L-NPC converter comprises two DC capacitors and wherein the controller is configured with an Equalization Model (EM) approach for injecting a Second Order Negative Sequence (SONS) current in the 3L-NPC converter when voltages of the two DC capacitors are not balanced, iteratively in order to balance the voltages.